Melting and metasomatism/refertilisation processes in the Patagonian sub-continental lithospheric mantle: A review

Autor: Massimiliano Melchiorre, Federico Casetta, Massimo Coltorti, Barbara Faccini, Mathieu Benoit, Michel Grégoire
Přispěvatelé: Consiglio Nazionale delle Ricerche, Università Italo Francese, Ministerio de Economía y Competitividad (España), Institute of Earth Sciences Jaume Almera, Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Dipartimento di Fisica e Scienze della Terra [Ferrara], Università degli Studi di Ferrara (UniFE), Géosciences Environnement Toulouse (GET), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Università degli Studi di Ferrara = University of Ferrara (UniFE), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)
Rok vydání: 2020
Předmět:
Zdroj: Digital.CSIC. Repositorio Institucional del CSIC
instname
Lithos
Lithos, Elsevier, 2020, 354-355, pp.105324. ⟨10.1016/j.lithos.2019.105324⟩
Lithos, 2020, 354-355, pp.105324. ⟨10.1016/j.lithos.2019.105324⟩
ISSN: 0024-4937
DOI: 10.1016/j.lithos.2019.105324⟩
Popis: The large amount of geochemical variability in peridotitic and pyroxenitic xenoliths exhumed by Eocene to present-day magmas in Patagonia provides a unique opportunity to investigate the depletion and enrichment processes affecting the lithosphere in proximity of subduction settings and their relationships with magmatism. In this study, a review of the geochemical features of the Patagonian ultramafic xenoliths coupled with new SrNd isotopic data on clinopyroxene separates from representative suites enabled us to delineate the main melt extraction and enrichment (metasomatism vs. refertilisation) processes acting in these sub-continental lithospheric mantle (SCLM) portions. Our findings show that clinopyroxenes and orthopyroxenes in Patagonian harzburgites/lherzolites lie on two discrete Al2O3/Mg# trends and record variable partial melting degrees (1–30%), progressively decreasing southward, where the mantle domains experienced melt extraction in the past. The occurrence of both negative and positive correlations between (La/Yb)N, SrN, and Al2O3 in clinopyroxenes suggests that large part of the SCLM beneath Patagonia was affected by both metasomatic (low melt-fluid/rock ratio) and refertilisation (high melt-fluid/rock ratio or long-lasting low melt-fluid/rock interaction) processes, while a few portions - particularly in Southern Patagonia - were devoid of significant enrichment processes. A comprehensive study of the major/trace element composition and rare earth element patterns of clinopyroxene from both cumulitic and mantle xenoliths led us to hypothesize that tholeiitic enrichment was followed by infiltration of transitional/alkaline agents in the Northern and Central Patagonian SCLM. The percolation of melts with transitional affinity can be identified in some Central Patagonian localities. In Southern Patagonia clinopyroxenes record a slight interaction with alkaline and proto-adakitic agents; the latter occurred at Cerro Fraile, the locality nearest the trench. The SrNd xenolith isotopic signature led to speculation that enriched and depleted mantle components interacted variably in the SCLM domain beneath Patagonia. This work suggests that a detailed and comprehensive study of ultramafic xenoliths can help identify the evidence produced by magmatic events occurring at the surface, as both a serial affinity and a temporal sequence.
This work is part of a co-tutorship Ph.D. held within the 2008 Vinci Project “Matter transfer in suprasubductivemantle in complex converging systems”. The project was funded by the Italian National Research Program [PRIN_2017 Project 20178LPCPW] to [MC], and by the “Università Italo-Francese”. The activities were conducted between the University of Ferrara and the Observatoire Midi-Pyrenees in Toulouse. MM appreciates the support of the project ALPIMED (PIE-CSIC- 201530E082). We thank the laboratory staff of the UMR 5563 (GET, Observatoire Midi-Pyrenees) of the University Paul Sabatier (Toulouse III) for their support during the performance of TIMS analyses.
Databáze: OpenAIRE
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